1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a single unit liquid crystal display touch panel and a method of fabricating the same. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for preventing a light leakage from lateral sides of the liquid crystal touch panel.
2. Discussion of the Related Art
A touch panel has been widely used for inputting a signal to a display surface of the display device without a supplementary input device such as a remote controller. Namely, a touch panel, which is installed on the display surface of a flat panel display device for an electronic pocket book, a liquid crystal display device (LCD), a plasma display panel (PDP), and an electroluminescent (EL) display device or an image display device, such as a cathode ray tube (CRT), so that a user can select information while enjoying an image.
Such touch panels are categorized into a resistive type, a capacitive type, an IR type, a photosensitive type, and the like.
A basic structure of the touch panel includes a transparent upper substrate having an upper electrode formed thereon and a transparent lower substrate having a lower electrode formed thereon to provide a predetermined space between the upper and lower substrates. Hence, once an input device such as a pen or a finger is contacted with a certain spot of the surface of the upper substrate, the upper electrode on the upper substrate is electrically connected to the lower electrode on the lower substrate. A control device then reads a voltage varied by a resistance or capacitance of the contacted spot and locates a coordinate of the contacted spot according to the voltage difference.
A single unit liquid crystal display (LCD) touch panel according to the related art is explained with reference to the attached drawings as follows.
FIG. 1 illustrates a schematic layout of a touch panel according to the related art. FIG. 2A illustrates a layout of metal electrodes and a signal line on the upper substrate in FIG. 1, and FIG. 2B illustrates a layout of metal electrodes and a signal line on the lower substrate in FIG. 1. FIG. 3 illustrates a cross-sectional view along line III-III in FIG. 1. And, FIG. 4 illustrates a cross-sectional view taken along line IV-IV in FIG. 1.
Referring to FIG. 1, a touch panel 100 in a liquid crystal display device according to the related art is divided into a viewing area VA corresponding to the display surface of the liquid crystal display device and a dead space DS formed on a peripheral part of the viewing area VA surrounded by the dead space DS.
Referring to FIGS. 3 and 4, transparent electrodes 3 and 4 are formed on the inner sides of upper and lower substrates 1 and 2 of the touch panel 100, respectively. And, the upper and lower substrates 1 and 2 are bonded to each other by an adhesive agent 9 on the dead space DS.
Hence, once a certain spot of the surface of the upper substrate 1 is contacted with a pen, finger, or the like, the transparent electrodes 3 and 4 are contacted with each other at the contacted spot, so that a varied voltage is output by a resistance value at the contacted spot. Since the voltage value varied by the resistance or capacitance value of the contacted spot must be read, a signal line 7 is formed to apply a voltage to the transparent electrodes 3 and 4 as well as read out the voltage value varied with a random contacted spot.
Referring to FIG. 2A, metal electrodes 5a and 5b are formed on the dead space DS of the left and right sides of the upper substrate 1 to be connected to the transparent electrode 3, respectively. And, a metal electrode 5c is formed on the upper or lower side of the dead space DS of the upper substrate 1. In this case, the metal electrodes 5a and 5b are electrically connected to the transparent electrode 3. Although the metal electrode 5c is electrically insulated from the metal electrode 5b, an insulating layer 10a is formed between the electrodes including the transparent and metal electrodes 3 and 5c, so that the metal electrode 5c is electrically insulated from the transparent electrode 3.
Referring to FIG. 2a and FIG. 4, the metal electrodes 5c and 5a are connected to the signal line 7 formed of flexible printed cable (FPC) through a conductive adhesive agent 8a. 
Referring to FIG. 2B, metal electrodes 6a and 6b are formed on the dead space DS of the upper and lower sides of the lower substrate 2 to be connected to the transparent electrode 4, respectively. And, a metal electrode 6c is formed on the left side of the dead space DS of the lower substrate 2. In FIG. 4, an insulating layer 10b is formed between the transparent and metal electrodes 4 and 6c, so that the metal electrode 6c is electrically insulated from the transparent electrode 4.
The signal line 7 is connected to the metal electrodes 6a and 6b on the dead space DS via the metal electrode 6c. Namely, the signal line 7 is electrically connected to the metal electrodes 5, 5b, and 6c by the conductive adhesive agents 8a and 8b. The signal line 7 applies a power or a ground voltage Vcc or GND to the transparent electrode 3 or 4 through the metal electrodes 5a, 5b, and 5c or 6a, 6b, and 6c or outputs a voltage output to the transparent electrode 3 or 4 when the upper and lower transparent electrodes 3 and 4 are electrically connected to each other at a random spot.
The metal electrodes 5a, 5b, and 5c or 6a, 6b, and 6c must be separated from the outermost side of the transparent electrode 3 or 4 by about 0.3 to 0.4 millimeters (mm) to prevent a short-circuit.
Thus, the signal line 7 and the metal electrodes 5a, 5c, and 6c are bonded to each other at a portion of the dead-space DS by the conductive adhesive agents 8a and 8b, and the upper and lower substrates 1 and 2 are bonded to each other in the dead space DS excluding for the portion of the dead space DS by a non-conductive adhesive agent 9.
In order to bond the signal line 7 to the metal electrodes 5a, 5c, and 6c, while the conductive adhesive agents 8a and 8b are disposed on the metal electrodes 5a, 5c, and 6c at portions where the signal line 7 is bonded, and the non-conductive adhesive agent 9 is disposed over an area of the dead space DS where the signal line 7 is not be bonded. About 100° C. as well as a pressure is selectively applied to the portions for bonding between the signal line 7 and the metal electrodes 5a, 5c, and 6c, so that the signal line 7 is bonded to the corresponding metal electrodes 5a, 5c, and 6c as soon as the upper and lower substrate 1 and 2 are bonded to each other.
FIG. 5 illustrates a cross-sectional view of a single unit LCD touch panel according to the related art.
Referring to FIG. 5, a single unit LCD touch panel includes a lower polarizing plate 51, a liquid crystal display panel having a lower substrate 30 formed on the lower polarizing plate 51 and an upper substrate 40 formed on the lower substrate 30, an upper polarizing plate 52 formed on the upper substrate 40 of the liquid crystal display panel, a touch panel 100 having a lower substrate 2 formed on the upper polarizing plate 52 and an upper substrate formed on the lower substrate 2. In addition, a case top 70 is formed on sides of the entire structure as described above and an upper circumference of the touch panel 100.
Color filter and thin film transistor arrays are formed on the upper and lower substrates 40 and 30 of the liquid crystal display panel, respectively. And, a liquid crystal layer (not shown) is formed between the substrates 40 and 30.
The components as described in FIGS. 2 to 4 are formed between the upper and lower substrates 1 and 2 of the touch panel 100.
The operation of the above-explained touch panel in liquid crystal display panel according to the related art is explained as follows.
First of all, when a pen, finger, or the like is contacted with a certain spot of the upper substrate 1 of the touch panel 100, the transparent electrodes 3 and 4 are contacted with each other at that spot. In this case, power and ground voltages Vcc and GND are applied to the left and right sides of the transparent electrode 3 through a pair of signal lines printed over the signal line 7 and the metal electrodes 5a, 5b, and 5c, respectively, and a voltage value of the contracted spot is read out through the transparent electrode 4 of the lower substrate 2, the metal electrodes 6a, 6b, and 6c, and a signal line printed under the signal line 7 to locate a coordinate value of the X-axis.
Besides, the power and ground voltages Vcc and GND are applied to upper and lower sides of the transparent electrode 4 through a pair of signal lines printed under the signal line 7 and the metal electrodes 6a, 6b, and 6c, respectively. A voltage value of the contracted spot is read out through the transparent electrode 3 of the upper substrate 1 and the metal electrodes 5a, 5b, and 5c to locate a coordinate value of the Y-axis. Hence, the X-Y coordinate values of the contacted spot are read out to obtain a position of the contacted spot.
FIG. 6 illustrates a layout of the single unit LCD touch panel according to the related art, in which the touch panel is divided into respective areas.
Referring to FIG. 6, a touch panel in a liquid crystal display panel using the liquid crystal display device as a display device has a liquid crystal display panel margin 33a greater than a dead space 33b of the touch panel in general. In this case, the margin 33a of the liquid crystal display panel is grater than that of the touch panel in considering a formation area of gate and data line driving parts formed under the liquid crystal display panel. Hence, the liquid crystal display panel margin 33a becomes a non-active area of the display device where a real circuit cannot be formed. An actual viewing area is an active area 31 of the liquid crystal display device, and this area becomes a display surface.
Problems or disadvantages of the above-explained single unit LCD touch panel according to the related art are explained as follows.
FIG. 7 illustrates a diagram for explaining problems of the touch panel in liquid crystal display panel according to the related art in FIG. 5, and FIG. 8 illustrates a diagram for explaining a principle of light leakage from the touch panel in liquid crystal display panel according to the related art in FIG. 5.
Referring to FIG. 7, a single unit LCD touch panel according to the related art includes a touch panel (elements between upper and lower substrates that are not shown in the drawing), which is constituted with the above-described upper and lower substrates 61 and 62, arranged-on the uppermost end, a liquid crystal display panel 30 and 40 under the touch panel, and a backlight unit 25 under the liquid crystal display panel 30. Moreover, a case top 70 is installed to surround the periphery of the touch panel including sides of the touch panel, the liquid crystal display panel 30 and 40, and the backlight unit 25.
The liquid crystal display panel includes an upper substrate having a color filter array formed thereon, a lower substrate 30 having a TFT array formed thereon, and a liquid crystal layer (not shown) injected between the upper and lower substrates 40 and 30. An upper polarizing plate 52 having the same size of the touch panel 60 is formed on the liquid crystal display panel 30 and 40 and a lower polarizing plate 51 is formed under the liquid crystal display panel 30 and 40.
In FIG. 7, the lower substrate 30 of the liquid crystal display panel has a margin M for the upper substrate 40 in considering an area where a driving unit for driving gate and data lines constructing the TFT array will be formed.
In order to minimize the influence on the screen display, the case top 70 is formed on the dead space as a non-viewing area of the touch panel, and has a gap of about 1.4 to 1.6 millimeters (mm) from an actual viewing area.
Hence, a portion of the light, which is indicated by a dotted line arrow, emitted from the backlight unit as an inner light source passes through the area of the margin M to penetrate a corner or lateral side of the touch panel 100, so that a light leakage toward the viewing area VA of the touch panel 100 may be caused.
Namely, when the light progressing in one direction through a first medium runs into a second medium of a transparent component such as the substrates 1 and 2, a refraction occurs at the interface between the first and second media and reflection and refracting keep occurring in progressing in the second medium.
Thus, in the single unit LCD touch panel according to the related art, the refractive or reflective light due to the lateral side and the corner of the touch panel causes the externally observed light leakage from the periphery of the display surface of the touch panel.